An ink-jet printer is an example of a printing device. Paper sheets after being printed by an ink-jet printer are ejected onto a paper sheet eject tray. When the paper sheets are in almost a full stack on the paper sheet eject tray, this state is detected as a near-full-stack state (near-full), and a user is warned of this state. When paper sheets are further ejected after being stacked up to the near-full state, the paper sheet eject tray will enter into the full-stack state. When the paper sheet stack tray is in the full-stack state, printing is interrupted. Then, a warning is given again to the user, and the printing is resumed after the paper sheets are removed from the paper sheet eject tray.
Here, when the paper sheets continue to be ejected further after the near-full state was detected, it is sometimes judged that the paper sheet eject tray is in the full-stack state, even though the paper sheet stack tray is not actually in the full-stack state. On this occasion, the printing is interrupted even though the printing device is still capable of stacking further paper sheets, and therefore productivity is reduced.
In view of the foregoing, a technology is disclosed in Patent Document 1 for recognizing a type of paper sheet, a residual capacity of a paper sheet eject base, or the like, and for calculating the number of remaining printable paper sheets so as to prevent printing from being interrupted during the printing of printing job data. In the technology described in Patent Document 1, a falling speed influenced by air resistance, or the like, is considered, and a stacking capacity on the paper sheet eject tray is estimated.
[Patent Document 1] Japanese Laid-Open Patent Publication No. 2010-89962